The invention relates to a brake cylinder having at least one brake chamber and a brake booster, actuatable by a piston rod, as generically defined hereinafter.
In brake cylinders now being installed in motor vehicles, brake boosters are typically provided between the brake pedal to be actuated and the corresponding brake chambers; after the brake pedal is actuated, these brake boosters generate a brake pressure independently of a brake force brought to bear. To this end, after brief actuation of the brake pedal, a pressure chamber connection to a reservoir or supply container is opened, and brake fluid is pumped out of the reservoir or supply container into the pressure chamber, for instance via a pump. The expanding pressure chamber puts a servo piston or the like under pressure, which transmits this pressure for instance to a piston in a brake chamber and thus reinforces the brake pressure.
Once the brake pressure has receded, a return line for the brake fluid present in the pressure chamber must be provided, so as to be able to relieve the servo piston or the like. A substantial factor in such brake boosters is the interplay between the opening or closing of the flow of brake fluid to the pressure chamber and the control of its return. Because of the many operative seals in such a structure the risk of leakage is very high. As a result, the servo pump must often pump power brake fluid out of the supply container to the reservoir, which requires energy and moreover cannot be done noiselessly.